Trk family proteins are receptor tyrosine kinases composed of three family members, TrkA, TrkB and TrkC. They bind with high affinity to, and mediate the signal transduction induced by the Neurotrophin family of ligands whose prototype members are Nerve Growth Factor (NGF), Brain-Derived Neurotrophic Factor (BDNF) and Neurotrophin 3-5 (NT 3-5). In addition, a co-receptor lacking enzymatic activity, p75, has been identified which binds all neurotrophines (NTs) with low affinity and regulates neurotrophin signaling. A critical role of the irks and their ligands during the development of the central and peripheral nervous systems have been established through gene disruption studies in mice. In particular, TrkA-NGF interaction was shown as a requirement for the survival of certain peripheral neuron populations involved in mediating pain signaling. It has been shown that increased expression of TrkA also correlates with an increased level of pain in the case of pancreatic cancer (Zhu, et al, Journal of clinical oncology, 17:2419-2428 (1999)). Increased expression of NGF and TrkA was also observed in human osteoarthritis chondrocytes (Iannone et al, Rheumatology 41:1413-1418 (2002)).
TrkA (Troponyosin-receptor kinase A) is a cell surface receptor kinase containing an extracellular, a transmembrane, and a cytoplasmic kinase domain. The binding of a neurotrophin triggers oligomerization of the receptors, phosphorylation of tyrosine residues in the kinase domain, and activation of intercellular signaling pathways, including Ras/MAPK cascade, PI3K/AKT, and IP3-dependent Ca2+ release. Tyrosine kinase activity is an absolute requirement for signal transduction through this class of receptor. NGF receptors have been also found on a variety of cell types outside of the nervous system. For example, TrkA has been also found on human monocytes, T- and B-lymphocytes and mast cells.
There are several examples of either anti-TrkA antibodies or anti-NGF antibodies known in the art. For examples, PCT Publication Nos. WO 2006/131952, WO 2005/061540 and EP 1181318 disclose use of anti-TrkA antibodies as effective analgesics in in-vivo animal models of inflammatory and neuropathic pain. PCT Application Nos. WO 01/78698, WO 2004/058184 and WO 2005/019266 disclose the use of an NGF antagonist for preventing or treating pain. PCT Application WO 2004/096122 describes a method for the treatment or the prevention of pain with co-administration of an anti-NGF antibody and an opioid analgesic. PCT Application WO 2006/137106 discloses a method for the treatment or the prevention of pain with co-administration of an anti-TrkA antibody and an opioid analgesic. In addition, profound or significantly attenuated reduction of bone pain caused by prostate cancer metastasis has been achieved by utilization of an anti-NGF antibody (Sevik, M A. et al, Pain 115:128-141 (2005)).
Loss-of-function mutations in TrkA (NTRK1) lead to congenital insensitivity to pain with anhidrosis [Nat Genet 1996; 13:485-8] and the anti-NGF antibody tanezumab has demonstrated clinical efficacy in osteoarthritis pain and diabetic neuropathic pain [N Engl J Med 2010; 363:1521-31: Arthritis Rheum 2013; 65:1795-803]. Additionally, Trk inhibitors show excellent efficacy in preclinical models of pain [Mol Pain 2010; 6:87-100]. Array has recently demonstrated equivalent efficacy with allosteric TrkA-selective inhibitors in pain models, which have the potential to be safer than pan-Trk inhibitors as discussed later [Array Website, 2012. Available from: http://www.arraybiopharrna.conm/_documents/Pubbcation/PubAttachment587.pdf [Last accessed 22 Jan. 2014]. There is some evidence that inhibition of Trks may be beneficial in the treatment of Alzheimer's disease. NGF and TrkA levels are elevated in airways of asthmatics (asthma) [J Asthma 2013; 50:712-17; Respirology (2009) 14, 60-68; and PLoS ONE 4(7): e6444. doi:10.1371/journal.pone.0006444] and may contribute to inflammation, hyperresponsiveness and remodeling. NGF and TrkA has also been shown to exacerbate ovalbumin-induced airway inflammation in rodents [Exp Ther Med 2013; 6:1251-8]. CT327 is a topical TrkA inhibitor that has been clinically evaluated by Creabilis for chronic pruritus in diseases such as atopic dermatitis, psoriasis and itch [http://clinicaltrials.gov/show/NCT1808157]. Inhibition of TrkA may have utility in the treatment of Chagas disease. Trypanosoma cruzi, the agent of Chagas' disease, utilizes Trk to invade various cell types in the human host [Infect Immun 2009; 77: 1368-75; Infect Immun 2011; 79:4081-7].
Selective inhibition of TrkA kinase activity may also have utility in the treatment of ear diseases [Laryngoscope 2011 October; 121(10):2199-213], liver cirrhosis and hepatocellular carcinoma [World J Gastroenterol 2007 Oct. 7; 13(37): 4986-4995], Pulmonary Inflammatory Diseases [Immunology and Microbiology>>“Inflammatory Diseases—A Modern Perspective”, book edited by Anit Nagal, ISBN 978-953-307-444-3, Published: Dec. 16, 2011, Chapter 5: Expression and Role of the TrkA Receptor in Pulmonary Inflammatory Diseases], fibrosis [J Cell Commun Signal. March 2010; 4(1): 15-23. Patent Application: PCT/GB2004/004795], Pterygium [Int. J. Exp. Path. (2009), 90, 615-620], lung diseases [Expert Rev Respir Med. 2010 June; 4(3): 395-411.], pulmonary sarcoidosis [Dagnell et al. Respiratory Research 2010, 11:156], bladder dysfunction [Neurourology and Urodynamics 30:1227-1241 (2011); BJU International 111, 372-380; J Urol. 2013 August; 190(2): 757-764; Neurourology and Urodynamics 33:39-45 (2014)], lower urinary tract dysfunction [International Journal of Urology (2013) 20, 13-20], Paget's disease [J Cutan Pathol 2010; 37: 1150-1154], diabetic nephropathy [Diabetes. September 2012, Vol. 61 Issue 9, p 2280-2288; Regulatory Peptides 135 (2006) 30-38.], irritable bowel syndrome [Neurogastroenterol Motil (2013) 25, e740-e754], radiation protection [Radiother Oncol. 2012 June; 103(3): 380-387.].
Furthermore, pain, which can be caused by the disease itself or by treatments, is common in people with cancer, although not all people with cancer will experience pain. Approximately 30% to 50% of people with cancer experience pain while undergoing treatment, and 70% to 90% of people with advanced cancer experience pain [Lesage P. and Portenoy R K. Cancer Control; Journal of the Moffitt Cancer Center 1999; 6(2):136-145]. Cancer pain is a complex, temporally changing symptom which is the end result of mixed mechanism pain. It involves inflammatory, neuropathic, ischemic, and compression mechanisms at multiple sites [Pathophysiology of cancer pain and opioid tolerance. In: The British Pain Society's Cancer Pain Management. The British Pain Society website. www.britishpainsociety.org. Published January 2010. Accessed Jan. 29, 2013]. It is a subjective, heterogeneous experience that is modified by individual genetics, past history, mood, expectation, and culture. Cancer pain syndromes are categorized as acute and chronic based on onset and duration. Acute pain syndromes have a sudden, well-defined onset, an identifiable cause (e.g. surgery), subject to sympathetic output (fight or flight response), and are expected to improve with management. Chronic pain on the other hand, has a less distinct onset, has a prolonged and fluctuating course, and is largely driven by central sensitization and neuroplastic responses from acute injury [Fornasari D. Pain mechanisms in patients with chronic pain. Clin Drug Investig 201; 32(suppl 1):45-52; Latremoliere A, Woolf C J. Central sensitization: a generator of pain hypersensitivity by central neural plasticity. J Pain 2009; 10:895-926]. It is often characterized by “pain flares” referred to as breakthrough pain [Portenoy R K, Dhingra L K. Assessment of cancer pain. In: Drews R E, ed. UpToDate. Waltham, Mass.: UpToDate; 2013].
The therapeutic implications of an effective Trk inhibitor may well go beyond pain therapy. A TrkA polymorphism has been identified to be associated with schizophrenia [J Psychiatr Res. 2009 October; 43(15):1195-9]. The subversion of this receptor and its signaling pathway in certain malignancies has also been documented. The potential utility of Trk inhibitors in oncology has been covered previously (for reviews, see, Expert Opin Ther Pat. 2014 July; 24(7):731-44; Nat Rev Cancer, 2004; 4:361-70; Clin Cancer Res, 2009; 15:5962-7). TrkA and/or Trk(B/C) have been implicated in the survival and metastasis of prostate [Expert Opin Investig Drugs, 2007; 16:303-9; Prostate, 2000; 45:140-8], breast [Cytokine Growth Factor Rev, 2012; 23:357-65], hepatocellular carcinoma (liver cancer) and liver cirrhosis [World J Gastroenterol. 2007 Oct. 7; 13(37):4986-95; Gastroenterology. 2002 June; 122(7):1978-86; Biochem Biophys Res Commun. 2011 Mar. 4; 406(1):89-95; Digestive Diseases and Sciences, Vol. 55, No. 10, (October 2010), pp. 2744-55, ISSN 0163-2116], intrahepatic cholangiocarcinoma [World J Gastroenterol 2014 April 14; 20(14): 4076-4084], liver fibrosis [Expert Rev Mol Med.; 11: e7. doi:10.1017/S1462399409000994], ovarian cancer [Gynecol Oncol. 2007 January; 104(1):168-75], pancreatic cancers [Clin Cancer Res., 2005; 11:440-9], oral cancer [Dermatol Surg 2004; 30:1009-1016] and oral cancer pain [J Dent Res 91(5):447-453, 2012], skin cancer [Am J Clin Pathol 2004; 122:412-420], cervical cancer [African Journal of Biotechnology Vol. 10(38), pp. 7503-7509, 25 Jul., 2011], bone cancer [J Vet Intern Med 2008; 22:1181-1188]. Other rare cancers such as congenital mesoblastic nephroma, infant fibrosarcoma [Am J Pathol, 1998; 153:1451-8] and secretory breast carcinoma [Cancer Cell, 2002; 347-8] carry Tel-TrkC gene rearrangements. Somatic rearrangements of TrkA have been detected in a small but consistent subset of papillary thyroid rumors [Cancer Lett 2006; 232:90-8; Mol Cell Endocrinol 2010; 321:44-9; Genomics. 1995 Jul. 1; 28(1):15-24; Int J Cancer. 1999 Mar. 15; 80(6):842-7].
An exciting new avenue in the field has recently opened with the discovery of oncogenic TrkA (NTRK1) rearrangements in a small subset of lung cancer patients [Nat Med 2013; 19:1469-72], and in colorectal cancer (as TPM3-TrkA funsion mutation) [Mol Oncol. 2014 Jun. 12. pii: S1574-7891(14)00125-2]. Tumor samples from 3 out of 91 lung cancer patients without previously identified genetic alterations demonstrated evidence of TrkA gene (NTRK1) fusions. These gene fusion mutations are intracellular oncogenic proteins, and they have constitutive activated intracellular TrkA kinase activity and transformed fibroblast cells. TrkA (NTRK1), TrkB (NTRK2), or TrkC (NTRK3) fusions have also been identified in glioblastoma, spitz tumors, spitzoid melanomas, acute myelogenous leukemia and secretory breast cancer [Greco A, et al. Mol Cell Endocrinol 2009; Alberti L, et al. J Cell Physiol 2003; Martin-Zanca D et al. Nature 1986; Wiesner T, et al. Nat Commun 2013; Vaishnavi A, et al, Nat Med 2013]. The identification of this gene rearrangement or fusion mutations may enable a patient stratification approach, similar to that utilized effectively by Pfizer, enabling the rapid registration and approval of crizotinib [Drugs 2013; 73:2031-51].
In fact, a patient with TrkA-positive metastatic colorectal cancer was recently clinically treated with RXDX-101, a pan Trk inhibitor and achieved a partial response [Ignyta, Inc. News Release. May 31, 2014. Website: http://finance.yahoo.cominews/ignyta-announces-interim-data-rxdx-190000889.html]. Our own search of public human cancer genomic databases uncovered that many types of human cancers have TrkA fusions or fusion mutations, for examples, breast cancer (e.g., CAL-51, CAMA-1 and other 3 human breast cancer cells from 5 patients), endometrial cancer (e.g., RK95-2 and other 7 human cancer cells from 8 patients), blood cancer (e.g., CML-T1 and other 3 cancer cells from 4 patients), liver cancer (SNU-878 and other 2 cancer cells from 3 patients), colorectal cancer (e.g., SNU-C4 and other 10 cancer cells from 11 patients), pancreatic cancer (e.g., pane 02.13 and panc 03.27 from 2 patients), and skin cancer (e.g., LOX IMVI and other 4 cancer cells from 5 patients), that a TrkA selective inhibitor like the ones disclosed in current invention or a compound of the present invention can be utilized to precisely inactive intracellular TrkA kinase activity in those constitutive activated intracellular oncogenic proteins, i.e., TrkA fusion mutations, and hence as an effective human cancer treatment therapy for the types of human cancers listed above.
The tyrosine kinase activity of Trk is believed to promote the unregulated activation of cell proliferation machinery. It is believed that inhibitors of TrkA, TrkB, or TrkC kinases, individually or in combination, have utility against some of the most common cancers such as brain, melanoma, multiple myeloma, squamous cell, bladder, gastric, pancreatic, breast, head, neck, esophageal, prostate, colorectal, lung, renal, ovarian, gynecological, thyroid cancer, and certain type of hematological malignancies. Lestaurtinib (CEP-701, Cephalon), an indolocarbazole inhibitor of several tyrosine kinases, including Flt-3 and TrkA, and CEP-751, a pan Trk inhibitor have been entered Phase II clinical trails for the treatment of acute myelogenous leukaemia (AML), pancreatic cancer and multiple myeloma (MM) and/or prostate cancer.
Of particular note are reports of aberrant expression of NGF and TrkA receptor kinase are implicated in the development and progression of human prostatic carcinoma and pancreatic ductal adrenocarcinoma and activating chromosomal rearrangements of Trks in acute myelogenous leukemia (AML), thyroid and breast cancers and receptor point mutations predicted to be constitutively activating in colon tumors. In addition to these activation mechanisms, elevated Trk receptor and ligand have also been reported in a variety of tumor types including multiple myeloma, melanoma, neuroblastoma, ovarian and pancreatic carcinoma. The neurotrophins and their corresponding Trk receptor subtypes have been shown to exert a variety of pleiotropic responses on malignant cells, including enhanced tumor invasiveness and chemotaxis, activation of apoptosis, stimulation of clonal growth, and altered cell morphology. These effects have been observed in carcinomas of the prostate, breast, thyroid, colon, malignant melanomas, lung carcinomas, glioblastomas, pancreatic carcinoids and a wide variety of pediatric and neuroectodermal-derived tumors including Wilm's tumor, neuroblastomas and medulloblastomas. Neurotrophins and their receptor subtypes have been implicated in these cancers either through autocrine or paracrine mechanisms involving carcinoma cells and the surrounding parenchymal and stromal tissues. Overall, the oncogenic properties of Trk signaling in multiple tumor types makes the modulation of the Trk receptor signaling a potentially attractive therapeutic intervention point in different malignancies.
Besides antibodies, however, few TrkA inhibitors are known and very few (if any) show high TrkA kinase selectivity (including staurosporine derived TrkA inhibitors, CEP-751 and CEP-701). It has been rarely known in the art that a synthetic organic molecule or compound had been used as either direct sub-type selective TrkA or NGF inhibitor or antagonist for treatment or prevention of pain in particular. It may due mainly to the facts of difficulty in identifying potent and particularly sub-type selective anti-TrkA or anti-NGF small organic compounds, though the crystal structure of NGF in complex with the TrkA receptor has been determined (Nature 401:184-188 (1996) & 254:411 (1991)).
Due to the therapeutic promise associated with inhibiting TrkA, and the relative lack of potent and selective inhibitors, it is great need to discover the potent and particular isoform selective TrkA inhibitors, especially of orally active small synthetic molecules for possible treatment or prevention of the disease or disorders associated with TrkA activity.
The free acid of compound 4-((3-(4-cyclohexylpiperazin-1-yl)-6-oxo-6H-anthra[1,9-cd]isoxazol-5-yl)amino)benzoic acid (“Compound 701”) and its pharmaceutical composition are known in US Patent Application No. 20110301133 A1 (corresponding PCT Patent Application, WO2009/067197, which is hereby incorporated by reference) and has the following chemical structure:

Compound 701, and the physiologically acceptable salts thereof, have valuable pharmacological properties. Compound 701 is a receptor tyrosine kinase inhibitor, particularly a potent NGF receptor TrkA inhibitor which, by virtue of its pharmacological properties, may be used, for examples, for the treatment and/or prevention of acute and chronic pain, cancer, restenosis, atherosclerosis, psoriasis, thrombosis, skin diseases, inflammation, inflammation related diseases, or a disease, disorder or injury relating to dysmyelination or demyelination. Other possible therapeutic applications can be found in WO2009/067197, the contents of which are hereby referred to.
Due to the limited solubility of the free acid Compound 701, it is very difficult to achieve practical oral bioavailability in the in-vivo systems, for example, in rat. Salt formation has been widely used in the art to improve lipophilic, water solubility and/or oral bioavailability, among other issues in the industry. However, it is problematic and huge challenge for selection and testing of the enormous numbers of possible salt forms in practice, since Compound 701 is zwitterionic molecule, there are vast amount of counterions and/or molecules that could form salts or co-crystals with Compound 701 and they can be from either (i) anionic counter-ions, for examples, acetate, benzoate, bicarbonate, bisulfite, norate, bromide, carbonate, chloride, citrate, formate, fumerate, glcuconate, glucuronate, hydrochloride, malate, nitrate, phosphate, salicylate, succinate and tartrate; (ii) cationic counter-ions, for examples, ammonium, piperazine, diethlyamine, diethanolamine, imidazole, diethylammonium, ethylenediamine, betaine, lithium, sodium, potassium, calcium, magnesium, aluminum, zinc, bismuth and stonium; or (iii) zwitterionic molecules, for examples, glycine, bicine, tricine, sulfamic acid, lysergic acid, and psilocybin. Furthermore, each salt or co-crystal forms may form various polymorphs with various degrees of physicochemical properties in terms of, for examples, solubility, stability, and oral bioavailability, it is therefore problematic and huge challenge in practice.
Another aspect which is important in drug development is that the active substance should have the most stable possible crystalline morphology for the pharmaceutical quality of a medicinal formulation. If this is not the case, the morphology of the active substance may change in certain circumstances under the conditions of manufacture of the preparation. Such a change may in turn affect the reproducibility of the manufacturing process and thus lead to final formulations which do not meet the high quality requirements imposed on pharmaceutical formulations. To this extent it should generally be borne in mind that any change to the solid state of a pharmaceutical composition which can improve its physical and chemical stability gives a significant advantage over less stable forms of the same drug.